Siloxanes are known to be effective polymer processing additives (PPAs). Low molecular weight polydimethyl silicone (PDMS) PPAs were reported as early as 1985 (see U.S. Pat. No. 4,535,113). Further, high molecular weight siloxane PPAs have more recently become available, for instance, from Dow Corning. The efficacy of these materials, however, is generally inferior to fluoroelastomer PPAs such as FX-9613 (available from 3M Company). Further, the tacky nature of such siloxane PPAs can make them difficult to handle and as such they are only provided as concentrates.
Siloxane block copolymers have also demonstrated efficacy as PPAs. For instance, 3M has developed a siloxane-polyamide PPA, and siloxane-polyurea block copolymers (SPU) are available from Wacker. These materials are thermoplastic and generally are more easily handled. Although effective as PPAs, they are typically less efficacious than fluoroelastomer based PPAs.
In practice, PPAs are added to melt-processable thermoplastic hydrocarbon polymers in order to improve their characteristics, for instance, in blow molding or injection molding. Such molded products often contain hindered amine light stabilizers.